The replacement of paper-and-pencil voting with an electronic system could see Australians lose confidence in the integrity of election results, the nation's electoral chief has warned.

Australian Electoral Commissioner Ed Killesteyn defended the current system's reliability following withering attacks from election hopeful Clive Palmer, who portrayed himself as a victim of ''rigged'' results and the Australian Electoral Commission as a military-infiltrated ''national disgrace''.

Despite the claims, Mr Palmer extended his lead over his Liberal National Party rival to 111 votes on Friday, with the final counting of outstanding votes in the Sunshine Coast seat of Fairfax expected on Saturday.

The Palmer United Party founder and wealthy Queensland businessman reacted angrily to the discovery of 750 votes tallied against the wrong pre-poll location mid-way through the count.

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In an earlier mistake, officials noticed 1000 votes for Victorian independent Cathy McGowan had not been recorded correctly, pushing the seat of Indi further out of reach of former Coalition frontbencher Sophie Mirabella, who subsequently conceded defeat this week.

Mr Killesteyn said computer-based voting would eliminate these kinds of ''human errors'' but the benefits would have to be weighed against hacking and manipulation fears.

He said 75,000 Australians helped to conduct federal elections and political party scrutineers watched the counting - a level of involvement designed to inspire community confidence.

''The notion that you could actually materially manipulate the result is, I think, quite implausible,'' he said on Friday.

''On the other hand, if you go to computer-based systems where everything is centralised, the risks start to increase that there could be significant manipulation of the results.''

Mr Killesteyn said numbering errors were picked up through normal checks comparing lower house and upper house ballot paper totals for each location.

''A lot has been made of the votes in Indi that were supposedly 'found' … and the same with Fairfax. Those votes were never lost. In the Indi case, it was a transcription error. That's all.

''The votes were properly secured. They were in a parcel. But when it was recorded in our election management systems a ''2'' became a ''1''. So that was fairly simple and that was picked up through our quality control processes.''

Mr Killesteyn said the correction of the pre-poll centre location for about 750 votes in Fairfax made no difference to the total number of votes already recorded for each candidate.

Playing down fears of manipulation by people voting more than once, Mr Killesteyn said senior citizens and those of non-English-speaking backgrounds were the groups most likely to mistakenly cast a ballot twice.

''We send people to all aged care facilities and so forth [to provide mobile voting centres]; they vote in that circumstance and then along comes the son or the daughter and says, 'Come on Mum, we've got to go voting', and they vote again on election day,'' he said. They were not systematic attempts to defraud the system.

Mr Killesteyn said the AEC had found 1500 instances of multiple voting at the 2010 election, or about 10 cases per electorate.

A discussion paper issued by the Electoral Council of Australia and New Zealand this week reignited the technology debate, suggesting it may be ''inevitable that paper balloting will, sooner or later, have to be replaced by some form of electronic voting''.